ebb vs diminution

ebb and diminution both are nouns.

Word	Noun	Adjective	Verb	Adverb
ebb	Yes	No	Yes	No
diminution	Yes	No	No	No

As nouns, diminution is a hypernym of ebb; that is, diminution is a word with a broader meaning than ebb:

Other hypernyms of ebb include decline.

ebb (noun)	diminution (noun)
the outward flow of the tide	the act of decreasing or reducing something
a gradual decline (in size or strength or power or number)	the statement of a theme in notes of lesser duration (usually half the length of the original)
	change toward something smaller or lower

ebb (verb)	diminution (verb)
fall away or decline
hem in fish with stakes and nets so as to prevent them from going back into the sea with the ebb
flow back or recede